Cycloturbine modular river current energy converter and method and apparatus for deploying marine hydrokinetic turbine assembly to harvest riverine and ocean tidal current energy

ABSTRACT

A hydrokinetic turbine system for harvesting energy from riverine and tidal sources, including a first floating dock, a marine hydrokinetic turbine mounted on the first floating dock, and a second floating dock. The system further includes a winch assembly mounted on the second floating dock and operationally connected to the first floating dock and a linkage assembly operationally connected to the first floating dock and to the second floating dock. The linkage assembly may be actuated to pull the first floating dock into contact with the second floating dock. The linkage assembly may be actuated to distance the first floating dock from the second floating dock, and the winch assembly may be energized to orient the first floating dock into a position wherein the marine hydrokinetic turbine is above the first floating dock and wherein the winch assembly may be energized to orient the first floating dock into a position wherein the marine hydrokinetic turbine is below the first floating dock.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority to co-pending U.S. Provisional Patent Applications 63/136,708 and 63/136,718, both filed on Jan. 13, 2022.

GOVERNMENT FUNDING

This invention was made with government support under DE-EE0008950 awarded by the Department of Energy. The government has certain rights in the invention.

BACKGROUND

The untapped energy carried by the rivers and oceans can potentially provide tens of millions of Americans with locally sourced, clean, and reliable energy, at a level over tens of Tera-Watts-Hour per year (TWh/yr). However, improving the technological, operational, and economic viability of marine and hydrokinetic (MHK) technology and gaining stakeholder acceptance are the two major obstacles to developing commercial-scale low-head river current energy converter (RCEC).

Among all the challenges experienced in developing RCEC systems, the high installation cost is a major one. MHK turbines in RCEC systems are usually installed using three different mounting options: bottom structure mounting (BSM), near-surface structure mounting (NSM), and floating structure mounting (FSM). The horizontal axis hydrokinetic turbines and similar designs often require massive and expensive civil work to construct BSM, which prevents their applications in most riverine applications. The systems utilizing FSM, on the other hand, require significant design effort and investment on the floating and mooring system, which draw an investment even higher than the turbine system itself, as manifested by the floating offshore wind systems. The design knowledge for FSM and NSM structures is very limited as compared with the knowledge for surface-mounted structures. To implement all these mounting options, the RCECs must be first transported to the working site, e.g., by tugboats. They will be then installed with the help of heavy-duty machines like crane boats or attached ballast systems.

In addition, traditional RCEC designs also suffer from high maintenance costs. For routine service (lubrication, changing fault parts, etc.), the entire system needs to be lifted out of the water with the help of a crane boat to gain dry assess, which significantly increases the maintenance cost, especially in remote sites.

The existing designs of RCECs suffer from low efficiency. Both the axial-flow and cross-flow turbines, when deployed in the low-head river current, demonstrate a suboptimal efficiency usually much lower than the theoretical Betz limit (59%) when no duct/diffuser augmentation is adopted. The design of vortex-induced vibration results in a measured efficiency of 28%, while the one using oscillating hydrofoils yields a peak efficiency of 40% at its optimal reduced frequency. The reported efficiency of the sails system is 25%. Failure to significantly improve the efficiency is attributed to the nature of the turbine system itself and also to the design tools that employ simplified models that are not adequate to analyze the complicated interaction between the running river current and rotating turbines.

In addition, traditional hydrokinetic turbines suffer from uneven hydrodynamic loading that is eventually born by the power train as fatigue loading and thus decreases the system reliability with increased maintenance cost.

Thus, there is a need for an improved hydrokinetic turbine and for an improved method and apparatus for deploying a hydrokinetic turbine to harvest energy from river currents. The present novel technology addresses these needs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cycloturbine modular river current energy transducer according to a first embodiment of the present novel technology.

FIG. 2 is a side elevation view of a linkage assembly portion of the cycloturbine modular river current energy transducer of FIG. 1.

FIG. 3A-3F schematically illustrates a method and assembly for positioning the cycloturbine modular river current energy transducer of FIG. 1 in a river.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the invention and presenting its currently understood best mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The novel MRCEC assembly adopts a three-section design of cycloidal turbine as shown in FIG. 1. A total of nine hydrofoils, three for each section (typically equidistantly spaced), take the hydrodynamic force when they are submerged into running river current. The MRCEC assembly three-section design also enables smooth energy harvest at different rotating phases so there are no oscillatory loads generated by the turbine.

High-fidelity computational fluid dynamics (CFD) simulations indicate that the hydrodynamic efficiency of this design reaches nearly 50%, significantly higher than other existing designs. The loads applied to the turbine support are nearly uniform over the entire revolution. The 3D cam mechanism also enables active control of the turbine operation so the turbine can be set at four different modes; (1) startup mode, where the hydrofoil pitch is adjusted to gain enough force to turn the turbine by the river flow, (2) high-efficiency mode, where the hydrofoil pitch scheme is set to harvest maximal energy at different income flow conditions, (3) constant power mode, where the turbine operates at the peak efficiency when the river flow is larger than the designed maximum flow speed, and (4) park mode, where the hydrofoil is controlled to generate large drag so the turbine does not rotate thus it is for easing on-site maintenance.

The present novel technology also contemplates a method of installing and servicing the MHK turbines to increase energy affordability and availability, in particular, to remote communities. This methodology features a unique approach that adopts two floating docks (a service dock and a turbine dock for mounting the MHK turbine). The entire system can be set at four different modes: transportation mode, installation mode, operation mode, and service mode, as shown in FIG. 3A-3F.

In the transportation mode, the MHK turbine sits on top of the turbine dock and is connected to the service dock. A tugboat tows the system to the preselected or desired working site or marina.

The installation mode is implemented in four steps (FIGS. 3B-3E). Once the assembly arrives at its predetermined working site, the mooring system is deployed to anchor the assembly in the middle of the river or ocean current. A linkage assembly maintains a safe distance between the two docks. A winch system is set up on the service dock and the cable is connected to the turbine dock. The winch is energized to flip the turbine dock and MHK turbine together until the turbine is completely submerged into water.

In the operation mode (FIG. 3F), the two docks are connected tightly. The turbine is actuated to harvest energy as designed.

In the service mode, the procedure in the installation mode is reversed so the turbine will be flipped out of the water to gain local dry access for service and maintenance.

Comparing to other existing designs, this new design offers a self-contained solution—it does not need to employ extra machines like a crane boat for installation and maintenance. It thus eases the operation and minimizes the installation and maintenance cost.

Additionally, the present system provides a novel cycloturbine-type modular river current energy converter (MRCEC) that can effectively harvest from the nation's rivers to increase energy affordability and availability, in particular, to remote communities.

Cycloidal turbines (cycloturbines) are designed to vary the blade pitch angle throughout each revolution to maximize the energy harvest. The traditional fixed-pitch Darrieus turbines often operate at angles of attack that either prevent power extraction or stall the blade during a portion of their revolution. These counterproductive aerodynamic forces attenuate available turbine power, cause damaging oscillatory loads, and prohibit self-start at a low rotational speed. Cycloidal turbines overcome these difficulties. However, the proper selection of blade pitching scheme is nontrivial and most of the previous efforts were based on a certain trial-and-error approach.

While the novel technology has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the novel technology are desired to be protected. 

What is claimed is:
 1. A hydrokinetic turbine system for harvesting energy from riverine and tidal sources, comprising; a first floating dock; a marine hydrokinetic turbine mounted on the first floating dock; a second floating dock; a winch assembly mounted on the second floating dock and operationally connected to the first floating dock; a linkage assembly operationally connected to the first floating dock and to the second floating dock; wherein the linkage assembly may be actuated to pull the first floating dock into contact with the second floating dock; wherein the linkage assembly may be actuated to distance the first floating dock from the second floating dock; wherein the winch assembly may be energized to orient the first floating dock into a position wherein the marine hydrokinetic turbine is above the first floating dock and wherein the winch assembly may be energized to orient the first floating dock into a position wherein the marine hydrokinetic turbine is below the first floating dock.
 2. The hydrokinetic turbine system of claim 1 and further comprising a mooring assembly connected to the first and second floating docks for securing the respective floating docks in place.
 3. A method of deploying a hydrokinetic turbine system in flowing water, comprising: a) positioning a first floating dock above flowing water; b) spacing a tethered second floating dock from the first floating dock; c) anchoring the first and second floating docks in place; d) energizing a winch mounted on the second floating dock to flip the first floating dock over to position a hydrokinetic turbine system mounted thereto in the flowing water; and e) connecting the first and second floating docks together.
 4. The method of claim 3 and further comprising: f) spacing the first and second platforms; and g) energizing the winch mounted on the second floating dock to flip the first floating dock over to position a hydrokinetic turbine system mounted thereto out of the flowing water.
 5. The method of claim 4 and further comprising: h) de-anchoring the first and second floating docks; and i) towing the hydrokinetic turbine system to another location.
 6. The method of claim 1 wherein the winch is operationally connected to a power source.
 7. A cycloidal turbine, comprising: a first section defining a first set of three operationally connected hydrofoils; a second section defining a second set of three operationally connected hydrofoils; and a third section defining a third set of three operationally connected hydrofoils; wherein the first, second, and third sections are operationally connected to one another; and wherein each respective section defines an independently variable pitch angle.
 8. The cycloidal turbine of claim 1 and further comprising: a cam; and a linkage assembly operationally connected to the cam and to each respective section; wherein the linkage assembly adjusts the rotating phase angels of each respective section.
 9. The cycloidal turbine assembly of claim 1 and further comprising: a plurality of water flow sensors arrayed about the cycloidal turbine; and an electronic controller operationally connected to the plurality of water flow sensors and to the linkage assembly; wherein the electronic controller induces the linkage assembly to independently vary the rotating phase angle of each section to optimize hydrofoil operating efficiency.
 10. The cycloidal turbine assembly of claim 1 wherein the electronic controller induces the linkage assembly to vary the rotating phase angle of each section to minimize oscillatory loads generated by the cycloidal turbine.
 11. The cycloidal turbine assembly wherein the linkage assembly may induce sections to be pitched for gaining enough force from flowing water to turn the turbine; wherein the linkage assembly may induce sections to be pitched for generating a maximum amount of energy from flowing water; and wherein the linkage assembly may induce sections to be pitched for not turning in response to flowing water.
 12. A cycloidal turbine assembly, comprising: a first set of three operationally connected hydrofoils; a second set of three operationally connected hydrofoils; a third set of three operationally connected hydrofoils; and a pitch-varying assembly operationally connected to the first, second, and third sets of operationally connected hydrofoils; wherein the pitch-varying assembly may adjust the pitch of each respective set of hydrofoils in response to ambient water flow conditions to define a unique pitch angle.
 13. A method of optimizing hydroelectric energy production, comprising: adjusting the pitch of a first set of hydrofoils; adjusting the pitch of a second set of hydrofoils; adjusting the pitch of a third set of hydrofoils; wherein each respective set of hydrofoils has a different pitch from the other respective sets of hydrofoils; wherein the first, second, and third respective sets of hydrofoils are operationally connected to define a cycloidal turbine.
 14. The method of claim 7 wherein each respective set of hydrofoils has a different rotating phase angle.
 15. The method of claim 8 wherein the respective phase angles of each respective set of hydrofoils are selected to maximize hydroelectric energy production.
 16. The method of claim 8 wherein the respective phase angles of each respective set of hydrofoils are selected to minimize oscillatory loading of the cycloidal turbine. 